java - 功能代码上的调试流跟踪抛出 IncompatibleClassChangeError

Question

当我尝试通过 IntelliJ 中的 Stream Trace 调试下面代码中的流时，调试器无法评估 foreach，因为抛出了下面的错误。我不知道它是关于什么的，代码本身运行良好。

完全更新了 IntelliJ 社区版、JUnit 5、Spring Boot、Maven、Java 11。

仅在 Stream Trace 调试期间发生的错误:

java.lang.IncompatibleClassChangeError: Type com.progonkpa.file.FileService$GeneratedEvaluationClass$5 is not a nest member of com.progonkpa.file.FileService: types are in different packages

包含流的代码:

public class FileService {

    public void createDirs(File parentDir, String[] fileNames) {
        Stream.of(fileNames)
                .map(fileName -> new File(parentDir, fileName))
                .forEach(file -> {
                    if (file.mkdirs())
                        System.out.println("Created file: " + file);
                    else
                        System.err.println("Failed to create file: " + file);
                });
    }
}

调用上述方法的测试:

public class FileServiceTest {

    private FileService fileService = new FileService();

    @Test
    public void generateDirs_createsList() {
        File tmpDir = new File("/tmp");
        String[] dirNamesList = {"dir1", "dir2"};
        File createdDir1 = new File(tmpDir, dirNamesList[0]);
        File createdDir2 = new File(tmpDir, dirNamesList[1]);

        fileService.createDirs(tmpDir, dirNamesList);

        assertTrue(createdDir1.exists());
        assertTrue(createdDir2.exists());
        assertTrue(createdDir1.delete());
        assertTrue(createdDir2.delete());
        assertTrue(tmpDir.delete());
    }
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.3.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.unknown.somefunction</groupId>
    <artifactId>joske</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <java.version>11</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <!--<dependency>-->
            <!--<groupId>org.springframework.boot</groupId>-->
            <!--<artifactId>spring-boot-starter-test</artifactId>-->
            <!--<scope>test</scope>-->
        <!--</dependency>-->
        <!--Data processing-->
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi</artifactId>
            <version>4.0.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>4.0.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-csv</artifactId>
            <version>1.6</version>
        </dependency>
        <dependency>
            <groupId>org.simplejavamail</groupId>
            <artifactId>simple-java-mail</artifactId>
            <version>5.1.3</version>
        </dependency>
        <dependency>
            <groupId>org.simplejavamail</groupId>
            <artifactId>outlook-message-parser</artifactId>
            <version>1.1.17</version>
        </dependency>
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.6</version>
        </dependency>
        <dependency>
            <groupId>com.github.vatbub</groupId>
            <artifactId>mslinks</artifactId>
            <version>1.0.5</version>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <version>5.3.2</version>
            <scope>test</scope>
        </dependency>
        <!--Testing-->

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

Answer 1

Stream 调试器显然生成字节码并动态定义类来计算表达式。相关源文件为

CompilingEvaluator.java
CompilingEvaluatorImpl.java

目前在 YouTrack 上有一个 Unresolved 问题，但有完全相同的异常(exception)情况

Type some.Type$GeneratedEvaluationClass$1 is not a nest member of some.Type: types are in different packages

IDEA-204665

这仅在大于 10 的 JDK 版本上表现出来，不幸的是你有

<java.version>11</java.version>

正如问题所暗示的那样，它发生是因为

JDK 11 has "Nest-based Access Control" feature
(https://cr.openjdk.java.net/~dlsmith/nestmates.html)

JEP 181说

Impact on Other Tools

Any tool that operates on classfiles, or which generates or processes bytecodes is potentially impacted by these changes. At a minimum such tools must tolerate the presence of the new classfile attributes and allow for the change in bytecode rules. For example:

The javap classfile inspection tool, The Pack200 implementation, and The ASM bytecode manipulation framework, which is also used internally in the JDK.